S1 fuel tank sending unit

[Certified Lotus]

I am in the midst of replacing the fuel tank in my S1. Have a replacement aluminum tank that has a baffle in the middle of the tank that prevents the sending unit float from being installed in the middle of the tank.

Has anyone installed a Caerbont automotive instruments variable length sending unit in their fuel tank? Any insights regarding the install would be very helpful!

[john.p.clegg]

Could you not just bend the arm to suit ??

John

[Certified Lotus]

The design allows you to shorten and solder the two metal rods together. I'm wondering who else has done this and if they have any insights.

[john.p.clegg]

As long as the float can sweep from top to bottom over the full travel of the sender unit you should be OK no matter how long/short/bent the arm is....

John

[Certified Lotus]

Thanks John. That is what I was thinking but wanted to confirm before I started cutting and soldering.

Has anyone installed one of these sending units? The instructions are limited and no info on the company web site. Just trying to hear what others experience has been.

[Certified Lotus]

Measured, cut and soldered the float arm so it was 1/2 inch from the baffle inside the tank. Installed the sending unit using fuel resistant sealant between the cork gasket and let it cure overnight.

[john.p.clegg]

Glen
Soldering the arm (s) together has effectively shortened it,will it still go to the top/bottom of the tank?

If not when it shows empty you'll have some left,and when showing full you'll have room for more...

John

[Certified Lotus]

John, I was concerned about the same. Did a test mounting it on a cardboard box with same dimensions before I cut and soldered the two arms together. Full range of motion. It should work without issues.

Installed the tank in my car, connected all the fuel lines, filled the tank with gas and went for a drive. No leaks! Now I have to get the right fittings and tidy up the whole install (it looks rather messy, but I didn't have all the fittings I needed).

Wiring the sending unit to the fuel gauge is next weekends project.

[Certified Lotus]

Last weekend I put 5 gallons of gas in the new tank and went for a 45 minute drive. Everything worked fine and no leaks. Last night I put another 5 gallons of gas in the tank, went for a 30 minute drive and after I park my car I notice fuel dripping from the boot. Check all the fittings and can't find a leak.

Then I run my hand around the sending unit plate and that's were its leaking. From everything I have read on this forum (thanks guys) my mistake is probably not using fiber washers (I used metal one) and not using fuel proof compound on the bolt threads.

So I will drain the tank, remove it and reseal it. Hopefully this time I will have done it right!

[vstibbard]

I always use a locktite or "Stag" sealer or similar fuel resistant thread lock for the bolts as well as the gasket

V

[Certified Lotus]

The saga continues. Drained the fuel tank, removed it from the car and guess what I found? The fuel was leaking through the spade connector fittings, not the gasket or the bolts! Seems the gasket material for the spade connectors disintegrated and caused the leak. I'm baffled. Wonder why/ how that happened?

[l10tus]

Watching this one with interest!

Did you fix the leak around the connectors (how?)

Did you manage to check if the Ohms readings were affecting the accuracy of the readings?

Where are you upto now?

Regards,

Phil.

[Certified Lotus]

Hi Phil, I was so involved in rebuilding my S1 last year (S1 Elan Rebuild - My Story) that I forgot to update this post. Sorry about that.

I removed the sending unit and sent it back to Dave Bean for a replacement as it was obvious that the little gaskets on the unit had leaked. They replaced it right away with a new one, which I then welded the float arm to the right length (as short as it will go) and installed on the tank. This time I used fuel resistant sealant on each of the bolts and threaded holes plus I put a thin amount of sealant on both sides of the cork gasket. Tightened everything up evenly and let it cure for 2 days before reinstalling the tank back in the car.

I also replaced the spade connectors on the wiring harness I had made for the sending unit to 90 degree angled versions so they wouldn't hit the back of the boot wall when the tank was in place.

This sending unit has a different load on it and the fuel gauge needs to be recalibrated to read correctly. I sent my fuel gauge to Dave Bean and they had it modified.

The tank has been in the car for 8 months now and a couple thousand miles of driving. No leaks. The gauge works well but I must have installed the float at a bit of an angle as it doesn't read 100% accurate (shows the tank more full than it really is). It's one my list of things to correct, remove the tank, take out the sending unit and bend the float arm a bit.

My suggestion is to have the gauge and dry tank hooked up so you can manually move the float arm and adjust in place. The real issue is the mounting of the sending unit as it needs to be bolted in only one way and the float location is critical.

Hope that explains it!